There are many different forms of data recording. For example, magnetic data recording is one of the prevailing forms of data recording. Magnetic data recording may be implemented using different types of magnetic recording media, including tapes, hard discs, floppy discs, etc. Over the years, significant developments have been made to increase the areal data recording density in magnetic data recording.
Superparamagnetism is a major limiting factor to increasing magnetic recording areal density. Superparamagnetism results from thermal excitations perturbing the magnetization of grains in a ferromagnetic material, making the magnetization unstable. As the magnetic media grain size is reduced for high areal density recording, superparamagnetic instabilities become more of an issue. The superparamagnetic effect is most evident when the grain volume V is sufficiently small that the inequality KuV/kBT>40 can no longer be maintained. Ku is the material's magnetic crystalline anisotropy energy density, kB is the Boltzmann's constant, and T is absolute temperature. When this inequality is not satisfied, thermal energy demagnetizes the individual grains and the stored data bits will not be stable. Therefore, as the grain size is decreased in order to increase the areal density, a threshold is reached for a given material Ku and temperature T such that stable data storage is no longer feasible.
The thermal stability can be improved by employing a recording medium formed of a material with a very high Ku. However, the available recording heads are not able to provide a sufficient or high enough magnetic writing field to write on such a medium. Heat Assisted Magnetic Recording (HAMR), sometimes referred to as optical or thermal assisted recording, has been proposed to overcome at least some of the problems associated with the superparamagnetic effect. HAMR generally refers to the concept of locally heating a recording medium with a laser to reduce the coercivity of the recording medium, so that an applied magnetic writing field can more easily direct the magnetization of the recording medium during the temporary magnetic softening of the recording medium caused by the laser. By heating the medium, the Ku or the coercivity is reduced such that the magnetic write field is sufficient to write to the medium. Once the medium cools to ambient temperature, the medium has a sufficiently high value of coercivity to assure thermal stability of the recorded information.
Current proposed HAMR head designs, which integrate a waveguide for facilitating coupling the light from the laser onto the recording medium, have a number of shortcomings. Some of the current head designs inefficiently couple the light from the laser. In some instances, a waveguide configuration with a size that is suitable for HAMR head is not suitable for efficient coupling of light from the laser. Some HAMR head designs require that the slider, which supports the head, have a sufficiently large back surface area in order to accommodate coupling of the light from the laser, which competes for space with the bonding pads of the slider. In addition, some of these head designs are difficult to fabricate.
Accordingly, there is a need for a HAMR head design that allows for efficient coupling of radiant energy into a waveguide, and that does not require large surface area of the slider. In addition, there is a need for a HAMR head design having a coupling to radiant energy, which does not substantially compete with the bonding pads for the back surface area of the slider. Furthermore, there is a need for a HAMR head design that lends itself for ease in manufacturing.